Refrigerating plant comprising piston operated compressor



Feb. 27, 1940. o. Z EHNDER 2,191,605 REFRIQERA'I'ING PLANT COMPRISING PISTON OPERATED COMPRESSOR Filed 'April 5, 1938 v 2 Sheets-Sheet 1 10 8. fave/2T0) 1 5 w; 5W I I Feb. 27, 1940.

o. ZEHIfIDER REFRIGERATING PILANT COMPRISING PISTON OPERATED COMPRESSOR Filed April 5, 1938 2 Sheets-Sheet 2 PatentedfFeh. t I

to Gebriider Zehnder Radiatoren- & Apparateban, Granichen, Switzerland r AppIication AprilS, 1938, Serial No. 200,232

I Germany April 9, 1937 8 Claims. (craz -4) This invention I relates to refrigerating plants comprising reciprocating piston type compressors.

In refrigerating plants comprising piston type compressors, 'as a rule, an electric motor drivingly connected with the refrigerant compressor by means 'of a belt drive is automatically connected with. or disconnected from 'a source of current asrequired by means of a relay or a thermostatic regulator, for the purpose of maintaining a predetermined :temperature in the refrigerator. When the electric motor is con-'- nected, the refrigerant gas is compressed in the compressor and displaced into the condenser wherein it is condensed while emitting heat. In most of the practical cases submerged coil evaporators are used in connection with which the compressor must produce sub-atmospheric pressure, so that evaporation of the refrigerant takes place in the evaporator until the desired temperature is established and the motor is disconnected. From this it follows that the com-' pressors operate periodically, in such manner,

that a' relatively long period of non-operation is followed by a period of uninterrupted operation of a relatively long duration also.

' With this mode of operation, the removal of "the heat of condensation and superheating is restricted to" a relatively short. time-and, since 0 the area of the surfaces concerned (compressor cylinder and condenser) is limited, high con-" densation temperatures and pressures as well as high cylinder temperatures result and thus accordingly detrimental influences on the wall 3 surfacesof thepompressor and condenser. Un-

der these circumstances the degree of efliciency of non-water coole'd refrigerating plants is considerably decreased. Also the presence of the belt drive'and the, unavoidable ventilation losses attending the mode of operation above explained further contribute to decreasing the degree of. efficiency of this type .ofqrefrigerating plant.

For practical reasons, such as, current impulses ifdue to=cutting inof switches; andrelay' energizing, the rating of the motor must not has been imparted a predetermined rotative be chosenftoo-high, in consequence of which .a

t f I relativelyihighrotatlve speed is required for the motor, in-orderlrto obtain the necessary refrige'rating'effe'ct :and adaptability of the aggregate.

' v It is further known to effect the suction stroke of.thecompressorpiston .by means of the pres- "sureofthe refrigerant'vapor entering the compressor .and thepressure stroke of the compressor. piston by means of an electric magnet, which is appropriately alternately connected and disconnected in automatic manner, whereby the output of the compressor is automatically controlled in accordance with fluctuations of demand for refrigeration of the plant. In this I a a decrease in the energyconsumption of 5 the plant and thus a corresponding economy in the costs of operation can be obtained, but owing to the current impulses which are set up, due to the cutting in of switches, the cylinder output, that is, the amount of refrigeration produced is restricted to a certain limit by the size of the electromagnetused, that is, the current consumption thereof. At the same time the. abrupt movements ofv the compressor piston caused by the electromagnet require unduly large 15 valve openings and correspondingly large cross sectional areas of the pressure piping's used, in order to avoid excessive pressure surges.

The present invention is concerned with a refrigerating plant comprising a piston type compressor the suction stroke of which is effected by the pressure of the refrigerant gas entering the compressor, whilst the compression stroke of the compressor is effected by electric; energy which is automatically controlled by switch means.

According to the present invention, the abovementioned drawbacks are eliminated in that, for the purpose of effecting the pressure stroke, -a plunger operated device cooperating with the compressor piston is automatically locked, when vthe'pressure of the refrigerant gas in the slic 4 tion conduit, is relatively low, and is automatically released, when the pressure of the refrigerant gas in the suction conduit attains a pre- 35 determined higher value, the shaft of an electric motor being rotated during the suction stroke by means of the piston rod, while the energising circult of the motor is interrupted and the energising circuit of the motor being closed while thepiston -moves through the respective end portion of stroke. I Therefore, since the electric .motor is electrically driven only while the compressor piston performs the pressure stroke, after the motor 46 'continuous control of the demand on refrigeration of the refrigerating plant. In practice low ll rotational speeds of the electric motor and thus relatively small numbers of strokes of the compressor piston may be applied, so that the com-. pressor and condenser are prevented from heating upexcessively. At the same time the heat developed is afforded ample time for dissipating, for the reason that thecycle of operation of the compressor is extended over a longer period. In this way, a very satisfactory degree of emciency of the refrigerant compressor is obtained which is further improved due to the belt drive and the ventilation losses being dispensed with. Again, a relatively cheap electric motor can be used owing to the motor circuit being closed only after the motor has been started by action of the compressor piston. Any type of short circuit armature motor, for example, the ordinary mono-phase induction motor with shortcircuited armature, is suitable.

The accompanying drawings servefor explaining the invention, by showing an embodiment of the same by way of example.

In the drawings, 4

Fig. 1 is a sectional elevation of a compressor,

- inclusive of accessories;

Fig. 2 is a larger scale section of a detail of the compressor;

Fig. 3 is an elevation, partly in section, taken at right angles to the plane of Fig. 1 and including the electric motor and parts of a toothed gearing;

Fig. 4 is a sectional view on the line'IV-IV of Fig. 1 on a larger scale.

Fig. 5 is a sectional view taken at right angles to the plane of Fig. 4 showing a gear wheel provided with a one-way clutch, and

Figs. 6 and 7 are detail views for explaining the In Fig. 1, the numeral I designates the condenser containing liquid ammonia, -.a lower conduit 2 leading-from the condenser to a temperature regulating device 3 which communicates with an evaporator 4 the other end of which is connected with the upper end of a. cylinder 5 forming part of a refrigerant compressor. The upper end of the cylinder 5 is further connected with the upper end of the condenser I through a conoperation of individual movable parts.

duit 5. The cylinder 5 is provided with acom- .pressor piston I which, under certain conditions of operation, moves up and down and which is provided with a packing ring 8 (Fig, 2) serving for the removal of oil and with an apron 9 consisting of a hygroscopic material, such as felt. Above the ring 8, a collar I consisting of a material resistant to oil, for example, a special rubber material, is arranged on the piston I as well as a headpiece ll which is situated inside of the collar so that, on the one hand, the lost space is accordingly reduced and, on the other hand, an open annular space I2 is formed within the collar (Fig. 2) which is filled with a special oil.

Above the collar III, on the headpiece II of the compressor piston 1 a further packing ring l3 for oil removal is arranged, for the purpose, of preven oil leakage in the direction towards the cylin er head, that is, towards the pressure side for the vapor. piston I dips each time, when moving downwards, into an oil supply I4 present in the closed lower end of the cylinder 5, thereby absorbing oil for lubricating the cylinder 5. Y The lower packing ring 8 on the compressor piston I also prevents the passage of an excess of oil. Owing to the oil within the cylinder having the tendency to flow downwardly to the most part, the supply of oil .tively (Fig. 2).

at 39 and is connected to a mercury tumbler The apron 9 of the compressor electric motor 44.

Y all times.

At the lower end of the cylinder a vent pipe I5 is arranged. In the head of the cylinder 5 5 spring loaded valve disks l5, II are correlated to the port openings of the connecting conduits to. the evaporator 4 and the condenser l respec- The two valve disks l5, H are displaceably arranged in associated recesses in the upper head of the cylinder 5, so that the disks can open and close in response to correspondingpressure influences. The valve seats l5a,, Ila, which consist of rubber, ensure that the respectlve port openings are tightly sealed against leakage of ammonia.

To the lower end of the guide rod l8 of the compressor piston 'l' is pivotally connected a rack l9 which forms an extension of this rod and is provided with oppositely disposed toothed portions 29, 2|. These toothed portions cooperate with pinions 22, 23 respectively. The pinion 22 is arranged on a shaft 24 with which it is connected by a one-way clutch 25 (Figs, 4, 5) so as to be driven by this shaft in one direction of rotation only, namely while the compressor piston I moves downwardly; thus by means of the rack l9. The pinion 23 is freely revolnbly arranged on a shaft 25 (Fig. 4). The hub 23' of the pinion 23 provides one portion of a claw clutch and can be moved into engagement with a second portion 21 of this clutch which rotates together with the shaft 25.

To this end the pinion 23 is provided with a circumferential groove which is formed in the hub thereof and which is engaged by a slot guide on a clutch control lever 28 which is mounted on a bolt 29 and carries a roller 30, at its outer end. The clutch control lever 28 cooperates, by means of the roller 30, with a cam slot 3| (Figs. 4, 6 and '7) which is provided with two oblique ascending faces 32, 33 and is formed by a projection 34 arranged on a side of the rack l9 which is devoid of gear teeth. The projection 34 is further pro vided with a guide face 35 (Figs. 6 and 7) which joins with an oblique face 35 to which a switching member 31 is correlated. J I

.A lever 38 cooperates with the faces 35, 35 and the switching member 3'! by means of a perpen- 'dicularly-bent up arm, this lever being mounted switch 40 and influenced by a tension spring 4|. The switch control lever 38 provides the armature of an electromagnet 42 one terminal of which is connected to the tumbler switch 40 by a lead, as shown in Fig. 3. The second terminal of the timibler switch 40 is connected to an electric motor 44 by a lead 43 (Fig. 3), further leads 45, 45 and 41 being associated with this motor, and a branch conductor 48 extending between the latter and the electromagnet 42, whereas the numerals 45, 41 designate line conductors of the network. The energizing circuit of the electric motor 44 is closed or broken by means of the tumbler switch-'45 depending upon conditions of operation. I

To the shafts 24, 25 are secured gear wheels 49, 50 respectively both of which are in mesh with an intermediate wheel 5| (Fig. 1). To the shaft 52 carrying the intermediate wheel 5| is secured a gear wheel 53 whiclrmeshes with a pinion 54 which is fixed to the shaft 55 of the A locking bar 56, which is rockably mounted on a pivot bolt 51, cooperates with the rack l9 1| f the compressor piston I. A tension spring 63 tends to retain .the locking bar .in the II, by means of aroller. A spring-loaded auxililever 66 cooperates with the locking bar. 66'

b'ymeans of a bentup. end and interenga'ges at the other end with a fork on a movablecontact member 66 which is correlated to a stationary The contact member is. arranged ,at the end of an elastic bellows 62 contact member 6|.

whichcan expand'in the direction of its longitudinal axis in a manner known per se, the other ofthe evaporator 4 through a conduit 63.

electromagnet 66 which is connected by'a'lead 66 with the stationary contact member 6|, the

second lead 61 of this magnet'being connected to the line conductor 46 of the supply circuit. A

.lead 66 connects the movable contact member "to the line conductor 41 of the supply circuit.

v The operation is as follows:

The plant is assumed to be in the condition of non-operation as depicted in Fig. 1.

If, for example, the refrigerator cabinet is opened and consequently the temperature rises in the same, the temperature regulating. device 3 allows liquid ammonia to pass from the condenser I into the evaporator 4 so that the [ammonia present in the evaporator begins to' vaporize, due to this heating eifect and the normal pressure of less than two atm. existing in the evaporator. By action of the pressure rise thus setting up in the conduit 63, the elastic bellows 62 is accordingly expanded, that is, clangated, in the direction of its longitudinal axis, so that the movable contact member 66 contacts with the stationary contact member 6|. Consequently, the electromagnet 65 is energized by current from the line 46, 4! of the circuit through the leads 66, 61 in which way the lateral projection 64 of the locking bar 56 is attracted so that the latter is rocked away. from the rack -then opened, of the cylinder 6, and the rack I6 is moved downwardlytogether with the piston.

This downward movement of the rack I6 is not obstructed by the pinion 23 for the reason that this pinion 23 is now movedoutof engagement with the clutch portion 21 by the clutch control lever 26, due to this lever having been corre- ,movement of the rack I6, bythe pinion 22 by l [means of the clutch 25 then being;operative.

.Therefore, the shaft 66 .of the electric; motor 44' .is rotated from the shaft 24 through 'the intermediary of the gear wheels .66, ll, 63 and .64; at a speed which depends upon the pressure of the refrigerant acting on the compressor piston I and accordingly reciprocating the piston at a corresponding speed. The motor is not connected at this time. Prior to the rack l9 arriving at its lowermost'position theswitch control lever 33slides along the oblique face 36 provided on the projection 34, whilst this, lever is rocked againstv the action of the spring, so that the mercurytumbler' switch "is tilted, in such a way, that contact is established between the two terminals of this switch and thus the energizing circuit of the motor is closed through the leads 41, 46, 43, 45 and 46, in consequence of which, the mechanical driving of the motor is changed over to electrical driving.

During the downward movement of the rack I6, shortly before arriving at its lowermost posi tion, the oblique ascending face 33 ofthe cam slot 3| eflects a rocking movement of the clutch control lever 26 to the right (Fig. 4) so that the clutch portion of'pinion 23- is moved into interengagement with the clutch portion 21 and the pinion 23 is thus operatively connected for rotation with the shaft 26 which is rotated from the intermediate wheel Si by the gear wheel 49. By the rotational movement, thus imparted to the pinion 23 from the electric motor 44, the rack I6 is moved upwardly. This upward movement of the. rack l6, and consequently also that of the compressor piston I, is not opposed by the pinion 22 which is now free to rotate in the opposite direction frombei'ore. I Due to the fact that the clutch 25 is now ineffective, the pinion 22 can freely rotate about the shaft 24.

During the upward movement of the compre'ssor piston I the latter cooperates with the condenser. I via the valve lI, then opened, of the cylinder 5. Accordingly, the rack I9 is moved upwardly whilst the switch control lever 38 slides over the switching member 31 then held in closed position, for. example,. by a leaf spring, and over a guideway 31" forming an extension of the switching member (Figs. 6 and 'I)I The switch control lever 36 moves clear of the guideway after the rack l6 has passed through approximately half the upstroke, the. switch control lever 38 being, however, prevented from rocking back under the'influenceof the associated spring 4|, due' to the force of attraction of the magnet 42 having been increased sufllciently, by an increase of the motor current, in the meantime, onaccount of the loading of the motor, for retaining the switch control lever 36 in position.

When the compressor piston I- has completed the compression stroke, the rack I9 is at its uppermost position, whilst the clutch control lever 26 has been rocked by the ascending face 32 of the cam slot 31, in such manner, that the pinion 2311s moved out of engagement with" the clutch portion 21. Consequently, the rotative connection between the pinion 23 and the shaft 26 is interrupted. As, at this time, the motor. is relieved, -the motor current is decreased instantaneously, in consequence of which the attractive forced the magnet 42 is accordingly decreased, whereupon the switch control lever 36 is retracted from the eleotromagnet 42, by action of the spring4l, and the mercury tumbler switch ,40 is disconnected,.sothat the motor circuit is interrupted. Provided that'the'pressure in the evaporator '4 is still .suiilciently high, the operation described will be repeated, whereby the motor 'atfirst,mechanicallydriven, namely, during the downward movement of the compressor piston I, whereas during the upward movement, that is,

during the compression stroke, the piston is driv-- en electrically. I

While the condition of operation described is maintained, the pressure of the refrigerant gas is naturally decreased. Under the influence of this pressure, the elastic bellows 62 is contracted so lyprojectirig arm the locking bar 56 issecured.

in inoperative position.

As the auxiliary lever 59 rocks back into initial position, the locking bar 56 swings back into 0perative position by action of the tension spring 58, for subsequently to obstruct the downward movementof the rack l9 and that of the compressor piston I, at the same time, until the pressure of the refrigerant gas has risen tosuch an extent that the elastic bellows 62 is sufliciently. expanded for moving the associated contact member into contact with the stationary contact member 6| whereupon the electromagnet 65 is again energised and the locking bar 56 is rocked out of operative position. In this way -the whole sequence of the further operations,

previously explained, is initiated.

Various changes and modifications may be made in the practice of my invention without' departing from the principle or spirit thereof,

by adding customary practice and established knowledge of the art to the. present disclosure and the -scope of the appended claims is not to be regarded as limited except as specified therein. I claim:

1. In an automatic refrigeration system, an evaporator, a condenser, a compressor having .a

reciprocable piston, a driving motor, a power transmission mechanism connecting the motor ,with said piston to drive the piston in the direction of its compression stroke, means for locking said transmission mechanism in such position as to hold said piston in a position removed from its extreme end position of compression, means responsive to the pressure of the refrigerant gas at the suction side of the compressor for controlling said locking means to effect locking when said pressure is below a predetermined pressure and to release said piston when the pressure exceeds a predetermined pressure, the suction stroke of the piston being then effected by the pressure of the refrigerant gas, and the rotation of the driving motor being initiated by the action of the piston, and means for automatically connecting said motor withv a source of electric power after the pistonhas initiated its rotation,

whereby the motor drives the compressor during its compression stroke.

2. Apparatus according to claim 1 and in which the means for controlling the locking means coinprises an electro-magnet and an electric switch for controlling the electro-magnet.

3. Apparatus according to claim 1 and in which the means for controlling the locking means com- 1 with said piston to drive thepiston in the direction of its compression stroke, a pivoted lever -for locking said transmission mechanism in such position as to hold the piston in a position in its expansion stroke spaced from its extreme end .being ly deenergized so that the position of compression, a second pivoted lever -for latching the first-mentioned lever in piston locking position, an electro-magnet, a switch for controlling the circuit of said magnet, said piston locking lever being within the field of influence of the electro-magnet, means responsive to-the pressure of the refrigerant gas at the suction side of the compressor for closing the switch of the electro-magnet and for tuming said latching lever to releasing position when said pressure .exceeds a predetermined pressure, and for opening said switch and pivoting said latching lever to piston locking position when said pressure falls below a predetermined pressure, whereby when the piston is released the suction stroke of the 7 piston and corresponding rotation of the motor are initiated by the pressure of the-expanded refrigerant gas, and means controlled by the movement of the piston in its suction stroke for connecting the motor with an electric circuit so that the piston is driven by the motor in its com-Q pression stroke.

- 5. In an automatic refrigeration system, an evaporator, a condenser, a compressor having a reciprocable piston, a driving motor, a power transmission mechanism connecting the motor with said piston to drive the piston in the direction of its compression stroke, means for look- '.ing said transmission mechanism in'such position as to hold said piston in a position spaced from said locking means to eifect locking when said pressure is below a predetermined pressure and 88 to release said piston when the pressure exceeds a predetermined pressure, the suction stroke of the pistonbeing then effected by the pressure of the refrigerant gas, and the rotation of the driving motor being initiated by the action of the '0 piston, and means including a mercury switch, an electro-magnet, a shift lever under the influence of said magnet and in position to be actuated upon inward movement of the piston, whereby the piston in its inward movement actuates the shift lever to move the mercury switch to closed position to close the circuit through the motor todrivethe piston in its compression stroke, the electro-magnet being strongly energized by the current of the motor during the com-- pression stroke so as to hold said shift lever and switch in closed position, the current drawn by said motor being reduced upon completion of the compression stroke and the electro-magnet' shift lever and mercury switch are released and the switch is opened and the motor circuit thus broken.

6'. In an automatic refrigeration system, an evaporator, a condenser, a driving motor, a compressor to be driven in its compression stroke by said motor, said compressor having a cylinder, a piston provided with an oil stripper ring extending therearound and with a sleeve below said ring, said sleeve having an annular oil chamber formed therein, a power transmission mechanism connecting the motor with said piston to drive the piston in the direction, of its compression stroke, means for locking said transmission mechanism so as to hold said piston in a position tion, means responsive to the pressure of the refrigerant gas at the suction side of the compressor for controlling said locking means to effect locking when said pressure is. below a ll 70 spaced from its extreme compression end posi- 1 k 8,191,605 predetermined pressure andto release said piston when the pressure exceeds a predetermined pressure, the suction stroke of the piston being then eflected by the pressure or the refrigerant gas, and the rotation of the driving motor being initiated by the action of the piston, and means for automatically connecting said motor with a 4 exhaust valve each having a rubber seat.

warm movement oi the piston;

8. Apparatus according to claim 1 and in which the compressor has a piston provided with a downwardly extending apron oi. hygroscopic material, and-the compressor has a cylinder provided with an oilreservoir in which the apron is immersed at the lower portion 01' the piston stroke, so that oil is raised by the apron and distributed over the walls of the cylinder upon up- OTTO ZEHNDER. 

